Add Hound/Rubocop config; Make Ruby style consistent

**Analog to opf/openproject#1879 and opf/openproject#2136**
Line is too long. [96/80]<br>Prefer `map` over `collect`.<br>Space missing after colon.<br>Space missing after comma.<br>Space found before comma.<br>Space between { and | missing.<br>Space missing inside }.